Use of salts of layered double hydoxides

ABSTRACT

A layered double hydroxide salt as a charge control agent in electrophotographic toners and developers, in powder coating materials, electret materials and in electrostatic separation processes of chargeable materials, such as polymers, wherein the double hydroxide salt contains monovalent and/or divalent, and also trivalent, metal cations, and also contains organic anions A of the formulae (I) to (XXX) set forth in the specification.

The present invention lies within the field of charge control agents,i.e., components which selectively influence electrostatic charging in amatrix.

In electrophotographic recording processes a latent charge image isproduced on a photoconductor. This latent charge image is developed byapplying an electrostatically charged toner which is then transferredto, for example, paper, textiles, foils or plastic and is fixed bymeans, for example, of pressure, radiation, heat or the action ofsolvent. Typical toners are one- or two-component powder toners (alsoknown as one- or two-component developers); also used are specialtytoners, such as magnetic toners, liquid toners or polymerization toners,for example. By polymerization toners are meant those toners which areformed by, for example, suspension polymerization (condensation) oremulsion polymerization and lead to improved particle properties in thetoner. Also meant are those toners produced basically in nonaqueousdispersions.

One measure of the quality of a toner is its specific charge q/m (chargeper unit mass). In addition to the sign and level of the electrostaticcharge, important quality criteria are the rapid attainment of thedesired charge level, the constancy of this charge over an extendedactivation period and the insensitivity of the toner to climaticeffects, such as temperature and atmospheric humidity. Both positivelyand negatively chargeable toners are used in copiers and laser printers,depending on the type of process and type of apparatus.

To obtain electrophotographic toners or developers having either apositive or negative charge, it is common to add charge control agents.Since the charge of toner binders is often heavily dependent on theactivation period, the function of a charge control agent is, on the onehand, to set the sign and level of the toner charge and, on the otherhand, to counteract the charge drift of the toner binder and to providefor constancy of the toner charge. Another important practicalrequirement is that the charge control agents should have sufficientthermal stability and effective dispersibility. Typical temperatures atwhich charge control agents are incorporated into the toner resins, whenusing kneading apparatus or extruders, are between 100° C. and 200° C.Accordingly, thermal stability at 200° C. is of great advantage. It isalso important for the thermal stability to be ensured over a relativelylong period (about 30 minutes) and in a variety of binder systems.

For effective dispersibility it is of advantage for the charge controlagent not to exhibit any waxlike properties or any tackiness and to havea melting or softening point of >150° C., better still >200° C.Tackiness frequently leads to problems in the course of metered additionto the toner formulation, and low melting or softening points may resultin failure to achieve homogeneous distribution in the course ofincorporation by dispersion, since the material amalgamates in the formof droplets in the carrier material.

Typical toner binders are addition polymerization, polyaddition andpolycondensation resins, such as styrene, styrene-acrylate,styrene-butadiene, acrylate, polyester and phenol-epoxy resins, and alsocycloolefin copolymers, individually or in combination, which may alsoinclude further components, examples being colorants, such as dyes andpigments, waxes or flow assistants, or may have these components addedsubsequently, such as highly disperse silicas.

Charge control agents may also be used to improve the electrostaticcharge of powders and coating materials, especially in triboelectricallyor electrokinetically sprayed powder coating materials as are used tocoat surfaces of articles made from, for example, metal, wood, plastic,glass, ceramic, concrete, textile material, paper or rubber. The powdercoating material, or the powder, receives its electrostatic charge, ingeneral, by one of the two following methods: In the case of the coronamethod, the powder coating material or powder is guided past a chargedcorona and is charged in the process; in the case of the triboelectricor electrokinetic method, the principle of frictional electricity isutilized. It is also possible to combine the two methods. The powdercoating material or powder in the spray apparatus receives anelectrostatic charge which is opposite to the charge of its frictionpartner, generally a hose or spray pipe made, for example, frompolytetrafluoroethylene.

Typical powder coating resins employed are epoxy resins, carboxyl- andhydroxyl-containing polyester resins, polyurethane resins and acrylicresins, together with the customary hardeners. Resin combinations arealso used. For example, epoxy resins are frequently employed incombination with carboxyl- and hydroxyl-containing polyester resins.

It has additionally been found that charge control agents are able toimprove considerably the charging and the charge stability properties ofelectret materials, especially electret fibers (DE-A43 21 289). Typicalelectret materials are based on polyolefins, halogenated polyolefins,polyacrylates, polyacrylonitriles, polystyrenes or fluoropolymers, forexample polyethylene, polypropylene, polytetrafluoroethylene andperfluorinated ethylene and propylene, or on polyesters, polycarbonates,polyamides, polyimides, polyether ketones, on polyarylene sulfides,especially polyphenylene sulfides, on polyacetals, cellulose esters,polyalkylene terephthalates, and mixtures thereof. Electret materials,especially electret fibers, can be used, for example, to filter (veryfine) dusts. The electret materials can receive their charge by coronaor triboelectric charging.

Additionally, charge control agents can be used in electrostaticseparation processes, especially in processes for the separation ofpolymers. Without charge control agents, the triboelectric chargingcharacteristics of low-density polyethylene (LDPE) and high-densitypolyethylene (HDPE) are extremely similar. Following the addition ofcharge control agent, LDPE takes on a highly positive and HDPE a highlynegative charge, and the materials can thus be separated easily. Inaddition to the external application of the charge control agents it isalso possible to incorporate them into the polymer in order, forexample, to shift the position of the polymer within the triboelectricvoltage series and to obtain a corresponding separation effect. In thisway it is possible to separate other polymers as well, such aspolypropylene (PP) and/or polyethylene terephthalate (PET) and/orpolyvinyl chloride (PVC), from one another.

Salt minerals can likewise be separated if they are admixed beforehand(surface conditioning) with an agent which improves thesubstrate-specific electrostatic charging (A. Singewald et al.,Zeitschrift für Physikal. Chem., vol. 124, pp. 223-248 (1981)).

Charge control agents are employed, furthermore, as “electroconductivityproviding agents” (ECPAs) (JP-05-163 449) in inks for inkjet printers.Additionally said double hydroxides are suitable for use as chargecontrol agents in color filters for additive or subtractive colorgeneration, and also in electronic inks for electronic newspapers.

Charge control agents can be used additionally for the surfacemodification of freeflow agents, such as highly disperse silicas intheir pyrogenic and precipitated forms, or metal oxides, such astitanium dioxide. In this case the effect is to optimize the physicalproperties, such as triboelectric charge behavior. Freeflow agents aremetered into the toner subsequently, in order to produce betterfree-flow properties.

U.S. Pat. No. 5,288,581 uses certain hydrotalcites as charge controladditives. JP 10-090 941 describes the use of a hydrophobicizedhydrotalcite as an external additive in combination with a positivecharge control agent. The primary purpose of that additive is to improvethe free-flow properties of the toner.

The object of the present invention was to find effective andecotoxicologically compatible charge control agents, featuring inparticular a high level of rapid charging and high charge stability.Furthermore, these compounds should be readily dispersible, withoutdecomposition, in various toner binders employed in practice, such aspolyesters, polystyrene-acrylates or polystyrene-butadienes/epoxy resinsand also cycloolefin copolymers. Furthermore, their action should belargely independent of the resin/carrier combination, in order to openup broad applicability. They should likewise be readily dispersible,without decomposition, in common powder coating binders and electretmaterials, such as polyesters (PES), epoxy, PES-epoxy hybrid,polyurethane, acrylic systems and polypropylenes.

In terms of their electrostatic efficiency the charge control agentsshould be active even at very low concentration (1% or less) and shouldnot lose this efficiency when in conjunction with carbon black or othercolorants. It is known of colorants that they can affect—in some caseslastingly—the triboelectric charging of toners.

Surprisingly it has now become evident that salts of layered doublehydroxides described below have advantageous charge control properties,especially for negative charging, and high thermal stabilities, thecharge control property being lost neither by combination with carbonblack nor by combination with other-colorants. Furthermore, thecompounds are readily compatible with the customary toner, powdercoating and electret binders and are easy to disperse.

The present invention provides for the use of layered double hydroxidesalts as charge control agents in electrophotographic toners anddevelopers, in powder coating materials, electret materials and inelectrostatic separation processes of chargeable materials, such aspolymers, wherein the double hydroxide salt contains monovalent and/ordivalent, and also trivalent, metal cations, and also contains organicanions A of the formulae (I) to (XXX)R₁—COO^(θ)  (I)R₂—COS^(θ)  (II)R₃—CS₂ ^(θ)  (III)R₆—SO₂ ^(θ)  (VI)

 ^(θOOC—R) ₁₀—COO^(θ)  (IX)^(θ)O₃SO—R₁₁—OSO₃ ^(θ)  (X)^(θO) ₃S—R₁₂—SO₃ ^(θ)  (XI)

in which

-   R¹ to R⁹ are identical or different and are CN, (CH₂)₁₋₈CN, halogen,    e.g., F, Cl or Br, branched or unbranched or cyclic C₁-C₄₄-alkyl,    mono- or polyunsaturated C₂-C₄₄-alkenyl,    C₁-C₂₂-alkoxy-(C₈-C₃₂)-alkylene, C₁-C₂₂-hydroxyalkyl,    C₁-C₂₂-carboxyalkyl-alkenyl, C₁-C₂₂-haloalkyl, C₂-C₂₂-haloalkenyl,    C₁-C₂₂-aminoalkyl, (C₁-C₁₂)-trialkylammonium-(C₁-C₂₂)-alkyl;    (C₁-C₂₂)-alkylene-(C═O)O—(C₁-C₃₂)alkyl,    (C₁-C₂₂)-alkylene-(C═O)O-aryl,    (C₁-C₂₂)-alkylene-(C═O)NH—(C₁-C₃₂)-alkyl,    (C₁-C₂₂)-alkylene-(C═O)NH-aryl,    (C₁-C₂₂)-alkylene-O(CO)—(C₁-C₃₂)alkyl, (C₁-C₂₂)alkylene-O(CO)-aryl,    (C, C₂₋₂)alkylene-NH(C═O)—(C₁-C₃₂)alkyl,    (C₁-C₂₂)-alkylene-NHCO-aryl, it being possible for    to be inserted into the acid ester or acid amide linkages,-   (C₁-C₃₂)alkylene-(C₆-C₁₄)aryl,    (C_(o)-C₃₋₂)alkylene(C₄-C₁₄)-heteroaryl with 1, 2, 3 or 4    heteroatoms from the group N, O and/or S,-   (C₁-C₂₂)alkylene-[(C₁-C₁₂)alkoxy]₀₋₁₀₀-[(C₁-C₁₂)alkoxy]₁₋₁₀₀-(C₆-C₁₄)aryl    or —(C₄-C₁₄)heteroaryl;-   R¹⁰ is a chemical bond or has one of the definitions of R¹¹ or R¹²;-   R¹¹ and R¹² are C₁-C₂₂-alkylene, mono- or polyunsaturated    c₂-C₂₂-alkenylene, mono- or polysubstituted C₁-C₂₂-hydroxyalkylene,    or C₁-C₂₂-hydroxycarboxy-alkylene,-   o- or m-(C₆-C₁₄)-arylene or (C₄-C₁₄)-heteroarylene with 1, 2, 3 or 4    heteroatoms from the group N, O and/or S, it being possible for the    rings independently of one another to be aromatic, unsaturated or    saturated and to carry further substituents as described below,    —(CH₂)₁₋₂₂—X—(CH₂)₁₋₂₂—,    —(CH₂)₁₋₂₂—O—CO—X—CO—O—(CH₂)₁₋₂₂—,    —(CH₂)₁₋₂₂—CO—O—X—O—CO—(CH₂)₁₋₂₂—,    —(CH₂)₁₋₂₂—NH—CO—X—CO—NH—(CH₂)₁₋₂₂—,    —(CH₂)₁₋₂₂—CO—NR—X—NR—CO—(CH₂)₁₋₂₂—,    in which X has the definition o-, p-, m-(C₆-C₁₄)-arylene,    (C₄-C₁₄)heteroarylene, (C₁-C₂₂)alkylene or (C₂-C₂₂)-alkenylene, and    R is hydrogen or (C₁-C₁₂)-alkyl;-   R¹³ is C₁-C₃₂-acyl, C₁-C₂₂-alkyl, C₂-C₂₂-alkenyl,    C₁-C₁₈-alkylene-C₆-C₁₀-aryl, C₁-C₂₂-alkylene-heterocycle,    C₆-C₁₀-aryl or (C₄-C₁₄)-heteroaryl having 1, 2, 3 or 4 heteroatoms    in the group N, O and/or S,-   R¹⁴ and R¹⁵ are C₁₋₁₈-alkylene, C₁-C₁₂-alkylene-C₆-C₁₀-arylene,    C₆-C₁₀-arylene, C₀-C₁₂-alkylene-heterocycle;-   R¹⁶ and R¹⁷ are hydrogen or one of the definitions of R¹ to R⁹;-   Z is —NH— or —O—;-   Y^(θ) is —COO^(θ), —SO₃ ^(θ), —OSO₃ ^(θ), —SO₂ ^(θ), —COS^(θ) or    —CS₂ ^(θ);    in which R¹⁸, R¹⁹ and R²⁰ are identical or different and are    hydrogen, C₁-C₂₂-alkyl, C₁-C₁₈-alkenyl, C₁-C₁₈-alkoxy,    hydroxy-(C₁-C₁₈)alkylene, amino-(C₁-C₁₈)alkylene, C₁-C₁₈-alkylimino,    carboxy(C₁-C₁₈)-alkylene, amino, nitro, cyano, sulfonic acid,    halogen, C₁-C₁₈-acyl, C₁-C₁₈-haloalkyl, C₁-C₁₈-alkylcarbonyl,    C₁-C₁₈-alkyl-carbonyloxy, C₁-C₁₈-alkoxycarbonyl,    C₁-C₁₈-alkylaminocarbonyl, C₁-C₁₈-alkyl-carbonylimino,    C₆-C₁₀-arylcarbonyl, aminocarbonyl, aminosulfonyl,    C₁-C₁₈-alkyl-aminosulfonyl, phenyl, naphthyl, heteroaryl, e.g.,    pyridyl, imidazolyl, triazinyl, pyrimidinyl;    and also heterocyclic compounds of the following formulae    in which the radicals R₁₀₀ to R₅₀₀ are identical or different and    are hydrogen, C, C₂₋₂-alkyl, C₁-C₁₈-alkenyl, C₁-C₁₈-alkoxy,    hydroxy-(C₁-C₁₈)alkylene, amino-(C₁-C₁₈)-alkylene,    C₁-C₁₈-alkylimino, carboxy, carboxy(C₁-C₁₈)-alkylene-, hydroxy,    amino, nitro, cyano, sulfo, halogen, C₁-C₁₈-acyl, C₁-C₁₈-haloalkyl,    C₁-C₁₈-alkylcarbonyl, C₁-C₁₈-alkylcarbonyloxy,    C₁-C₁₈-alkoxycarbonyl, C₁-C₁₈-alkylaminocarbonyl,    C₁-C₁₈-alkylcarbonylimino, C₆-C₁₀-arylcarbonyl, aminocarbonyl,    aminosulfonyl, C₁-C₁₈-alkylaminosulfonyl, phenyl, naphthyl,    heteroaryl, e.g., pyridyl, imidazolyl, triazinyl, pyrimidinyl;    and in which in the heterocyclic compounds (XXIII) to (XXX) the    atomic groups A to F are a constituent CH₂, CH, C═O, N, NB, NH,    NH^(⊕), NH₂ ^(⊕), O or S of a heteroaromatic, unsaturated or    saturated heterocyclic compound, at least one of the groups A to F    being a carbon-containing group.

Unless otherwised described “aryl” in the definitions above and below ispreferably C₆-C₁₈-aryl, especially phenyl or naphthyl. “Heteroaryl” or“heterocycle” is preferably a saturated, unsaturated or aromatic, five-to seven-membered ring having 1, 2, 3 or 4 heteroatoms from the group N,O and/or S, such as, for example, pyridyl, imidazolyl, triazinyl,pyridazyl, pyrimidinyl, pyrazinyl, piperidinyl, morpholinyl, purinyl,tetrazonyl, pyrrolyl. Additionally the aryl and heterocyclic radicalsmay be substituted one or more times, such as 2, 3, 4 or 5 times, forexample, on carbon atoms or heteroatoms by C₁-C₂₂-alkyl, C₁-C₁₈-alkenyl,C, C₁₈-alkoxy, hydroxy-(C₁-C₁₈)alkylene, amino-(C₁-C₁₈)alkylene,C₁-C₁₈-alkylimino, carboxy, carboxy(C₁-C₁₈)-alkylene-, hydroxy, amino,nitro, cyano, sulfonic acid, halogen, C₁-C₁₈-acyl, C₁-C₁₈-haloalkyl,C₁-C₁₈-alkylcarbonyl, C₁-C₁₈-alkyl-carbonyloxy, C₁-C₁₈-alkoxycarbonyl,C₁-C₁₈-alkylaminocarbonyl, C₁-C₁₈-alkyl-carbonylimino,C₆-C₁₀-arylcarbonyl, aminocarbonyl, aminosulfonyl,C₁-C₁₈alkylaminosulfonyl, phenyl, naphthyl, heteroaryl, e.g., pyridyl,imidazolyl, triazinyl, pyrimidinyl.

Particularly preferred anions are

in which R is hydrogen, C₁-C₄-alkyl, C₁-C₄-alkoxy or halogen.

Compounds in this sense are, for example, the anions of the followingacids: benzoic acid, naphthoic acid, 4-tert-butylbenzoic acid, phthalicacid, isophthalic acid, sulfoisophthalic acid, benzenesulfonic acid,p-toluenesulfonic acid, p-dodecylbenzenesulfonic acid, benzenedisulfonicacid, naphthalenesulfonic acid, 2,2′-dithiobenzoic acid,tert-butylsalicylic acid, di-tert-butylsalicylic acid,3-pyrroline-2-carboxylic acid, N-(4-carboxyphenyl)pyrrole,pyrrole-2-carboxylic acid, pyrrole-3-carboxylic acid,imidazole-1-carboxylic acid, imidazole-2-carboxylic acid,imidazole-4-carboxylic acid, imidazole-4,5-dicarboxylic acid,2-imidazolidinone-4-carboxylic acid, pyrazole-4-carboxylic acid,pyrazole-3,5-dicarboxylic acid, pyridine-2-carboxylic acid,pyridine-3-carboxylic acid, pyridine-4-carboxylic acid,pyridine-2,3-dicarboxylic acid, pyridine-2,4-dicarboxylic acid,pyridine-2,5-dicarboxylic acid, pyridine-2,6-dicarboxylic acid,pyridine-3,4-dicarboxylic acid, pyridine-3,5-dicarboxylic acid,pyrimidine-2-carboxylic acid, pyrimidine-2,4-dicarboxylic acid,pyridazine-3,6-dicarboxylic acid, pyridazine-3-carboxylic acid,pyrazine-2-carboxylic acid, pyrazine-2,3-dicarboxylic acid,2-pyrrolidinone-5-carboxylic acid, piperidine-2-carboxylic acid,piperidine-3-carboxylic acid, piperidine-4-carboxylic acid,piperazine-2-carboxylic acid, piperazine-2,3-dicarboxylic acid.

In said double hydroxide salt the number of hydroxyl groups isapproximately from 1.8 to 2.2 times, preferably about 2 times, the sumof all the metal cations. The molar ratio of the monovalent and/ordivalent metal cations to the trivalent metal cations can be between 10⁴and 10⁻⁴, preferably between 10 and 0.1, in particular between 5 and0.2.

The ratio of the monovalent to the divalent metal cations can bearbitrary, but it is preferred for double hydroxide salts to be presentwhich contain exclusively divalent metal cations or a mixture ofmonovalent and divalent metal cations. A can be a singly or multiplycharged organic anion. The amount of the anions A is determined by thestoichiometry of the positive and negative charges in the doublehydroxide salt such that the sum of all charges produces zero. It is,however; possible for some of the anions, for example, from 0.1 to 99mol %, in particular from 1 to 90 mol %, to be replaced by other anions,such as inorganic anions, for example, such as halide, carbonate,sulfate, nitrate, phosphate or borate.

The double hydroxide salts used in accordance with the invention mayalso contain water molecules in the form of water of crystallization orintercalated between individual layers.

Suitable monovalent metal cations include particularly alkali metalcations, such as Li⁺, Na⁺ or K⁺.

Suitable divalent metal cations include particularly Mg²⁺, Ca²⁺, Zn²⁺,Co²⁺, Ni²⁺, Fe²⁺, Cu²⁺ or Mn²⁺.

Suitable trivalent metal cations include particularly A ³⁺, Fe³⁺, Co³⁺,Mn³⁺, Ni³⁺, Cr³⁺ and B³⁺.

Particularly preferred double hydroxide salts are those containing Mg²⁺and Al³⁺, especially in a molar ratio of from 3.1:1 to 1:2.

Starting products for double hydroxides for the purposes of the presentinvention are hydrotalcites, which are mostly available commercially andcontain an inorganic anion, mostly carbonate. By means of suitablemethods, such as reaction in aqueous, organic, e.g., alcoholic, oraqueous-organic suspension with the corresponding organic anions, in theform for example of their salts, the double hydroxide salts used inaccordance with the invention can be prepared from these commercialproducts.

In one preferred embodiment the hydrotalcite thus prepared is calcined,i.e., heated to a temperature of 150 to 1000° C., where appropriateunder reduced pressure.

Particular preference is given to double hydroxide salts having a molarratio Mg:Al of about 3:1, about 2:1, about 5:4 or about 1:2, and also tothe calcined forms thereof.

The salts of layered double hydroxides are prepared advantageously in anaqueous medium at a pH of from 3 to 14 and at a temperature of between 0and 100° C., preferably with stirring and where appropriate underpressure as well. The preparation can also take place where appropriateunder autoclave conditions, i.e., under pressures of between 1.1 and1000 bar, preferably between 1.1 and 500 bar, in particular between 1.1and 200 bar, and at temperatures between 20 and 200° C., preferablybetween 30 and 190° C., in particular between 40 and 180° C. The organicanion or anions used are advantageously employed in equimolar amounts,although a deficit of 0.1 to 99.9% is also possible. The organic anionscan be used directly in salt form, for example, as the sodium orpotassium salt, or else as the acid in the protonated form, and in thelatter case it may be necessary to adjust the pH by means of a base suchas sodium or potassium hydroxide or carbonate, for example, in order toensure a better distribution of the acid in the aqueous medium. Theorganic anions may additionally be used as acid halides, as acidanhydrides, as acid azides or esters of acids. This applies inparticular for preparation in organic solvents.

The compounds described in accordance with the invention can also beprepared by direct reaction of the calcined or uncalcined doublehydroxides with the corresponding organic acids or salts thereof, withheating, in a mixing apparatus, such as in a kneading apparatus,extruder, dissolver, bead mill, Henschel mixer or other mill, forexample. Also possible is preparation by reacting salts of thedouble-hydroxide-building metal cations, such as magnesium chloride andaluminum chloride, in aqueous alkali metal hydroxide solution, with theacid or the salt of the organic anions.

The salts of layered double hydroxides used in accordance with theinvention can be matched precisely to the particular resin/toner system.A further technical advantage of these compounds is that they are inerttoward the various binder systems and can therefore be employeddiversely, it being particularly significant that they are not dissolvedin the polymer matrix but rather are present as small, very finelydivided solid structures. Furthermore, they exhibit high and often: veryconstant charge control properties and also very good thermalstabilities. Moreover, the double hydroxides used in accordance with theinvention are free-flowing and possess effective dispersibility.

Dispersion means the distribution of one substance within another, i.e.in the context of the invention the distribution of a charge controlagent in the toner binder, powder coating binder or electret material.

It is known that crystalline substances in their coarsest form arepresent as agglomerates. To achieve homogeneous distribution within thebinder, these agglomerates must be disrupted by the dispersing operationinto smaller aggregates or, ideally, into primary particles. Theparticles of charge control agent present in the binder followingdispersion should be smaller than 1 μm, preferably smaller than 0.5 μm,with a narrow particle size distribution being of advantage. For theparticle size, defined by the d₅₀ value, there are optimum ranges ofactivity depending on the material. For instance, coarse particles (1mm) can in some cases not be dispersed at all or can be dispersed onlywith considerable investment of time and energy, whereas very fineparticles in the submicron range harbor a heightened safety risk, suchas the possibility of dust explosion.

The particle size and form is established and modified either by thesynthesis and/or by aftertreatment. The required property is frequentlypossible only through controlled aftertreatment, such as milling and/ordrying. Various milling techniques are suitable for this purpose.Examples of advantageous technologies are airjet mills, cutting mills,hammer mills, bead mills and impact mills.

The binder systems mentioned in the present invention are, typically,hydrophobic materials. High levels of water in the charge control agentcan either oppose wetting or else promote dispersion (flushing). Thepracticable moisture content is therefore specific to the particularmaterial.

The compounds of the invention feature the following chemical/physicalproperties:

The water content, determined by the Karl-Fischer method, is mostlybetween 0.001 and 30%, preferably between 0.01 and 25% and, withparticular preference, between 0.1 and 15%, it being possible for thewater to be in adsorbed and/or bound form, and for its proportion to beadjusted by the action of heat at up to 200° C. and reduced pressuredown to 10⁻⁸ torr or by addition of water, or by storage under definedair humidity conditions.

Surprisingly the compounds used in accordance with the invention,containing one or more above-defined organic anions, exhibit noparticular increase in H₂O content (Karl-Fischer method) following 48 hstorage at 90% relative air humidity at 25° C. in a conditioning testcabinet, while the analogous double hydroxides with inorganic anionshave much higher H₂O contents, in some cases a multiple of that prior toconditioning storage.

The particle size, determined by means of evaluation by light microscopyor by laser light scattering, and defined by the d₅₀ value, is between0.01 μm and 1000 μm, preferably between 0.1 and 500 μm, and with veryparticular preference between 0.5 and 400 μm. It is particularlyadvantageous if milling results in a narrow particle size. Preference isgiven to a range Δ (d₉₅-d₅₀) of less than 500 μm, in particular lessthan 400 μm.

The conductivity of the 5% aqueous dispersion is between 0.001 and 2000mS, preferably between 0.01 and 100 mS. The compounds of the inventioncontain predominantly crystalline fractions but also amorphousfractions. The compounds used in accordance with the invention,incorporated into a toner binder, show a temperature stability up to200° C. (no discoloration) in a thermal gradient test (Kofler test).

In the case of electrokinetic surface potential determination by meansof SCD (streaming current detection), the compounds used in accordancewith the invention surprisingly exhibit much lower surface potentials(positive or negative sign) than the corresponding double hydroxideswith inorganic anions. When these compounds are titrated withcorresponding surface-active reagents to the zero point of the surfacepotential (SCD monitoring of the titration), the amount ofsurface-active reagent required in the case of the compounds withinorganic anions is significantly higher than in the case of thecorresponding double hydroxides with organic anions. This points to arelatively high stability of the salt bond between double hydroxide andorganic anion.

The salts of layered double hydroxides employed in accordance with theinvention can also be combined with further positive or negative chargecontrol agents in order to obtain good performance chargeabilities, theoverall concentration of the charge control agents being advantageouslybetween 0.01 and 50% by weight, preferably between 0.05 and 20% byweight, with particular preference between 0.1 and 5% by weight, basedon the overall weight of the electrophotographic toner, developer,powder or powder coating material.

Examples of suitable further charge control agents are:triphenylmethanes; ammonium and immonium compounds, iminium compounds;fluorinated ammonium and fluorinated immonium compounds; biscationicacid amides; polymeric ammonium compounds; diallylammonium compounds;aryl sulfide derivatives, phenol derivatives; phosphonium compounds andfluorinated phosphonium compounds; calix[n]arenes, cyclically linkedoligosaccharides (cyclodextrins) and their derivatives, especially boronester derivatives, interpolyelectrolyte complexes (IPECs); polyestersalts; metal complex compounds, especially salicylate-metal complexesand salicylate-nonmetal complexes, salts of ionic structured silicates,hydroxycarboxylic acid-metal complexes and hydroxycarboxylicacid-nonmetal complexes, benzimidazolones; azines, thiazines oroxazines, which are listed in the Colour Index as Pigments, SolventDyes, Basic Dyes or Acid Dyes.

Particular preference is given to the charge control agents specifiedbelow, which can be combined individually or in combination with oneanother with the double hydroxides used in accordance with theinvention:

-   triphenylmethanes, as described for example in U.S. Pat. No.    5,051,585; ammonium and immonium compounds, as described for example    in U.S. Pat. No. 5,051,676;-   fluorinated ammonium and fluorinated immonium compounds, as    described for example in U.S. Pat. No. 5,069,994; biscationic acid    amides, as described for example in WO 91/10172; diallylammonium    compounds, as described for example in DE-A-4 142 541, DE-A4 029 652    or DE-A4 103 610;-   aryl sulfide derivatives, as described for example in DE-A4 031 705;-   phenol derivatives, as described for example in EP-A-0 258 651;-   phosphonium compounds and fluorinated phosphonium compounds, as    described for example in U.S. Pat. No. 5,021,473 and U.S. Pat. No.    5,147,748;-   calix[n]arenes, as described for example in EP-A-0 385 580;-   benzimidazolones, as described for example in EP-A-0 347 695;-   cyclically linked oligosaccharides, as described for example in    DE-A-4 418 842; polyester salts, as described for example in DE-A4    332 170;-   cyclooligosaccharide compounds, as described for example in DE-A-197    11 260;-   interpolyelectrolyte complexes, as described for example in DE-A-197    32 995;-   salts of ionic structured silicates, as described for example in    PCT/EP00/1 1217. Also suitable, especially for liquid toners, are    surface-active, ionic compounds and those known as metal soaps.

Particularly suitable are alkylated arylsulfonates, such as bariumpetronates, calcium petronates, barium dinonyinaphthalenesulfonates(basic and neutral), calcium dinonylsulfonate or Nadodecylbenzenesulfonate, and polyisobutylenesuccinimides (Chevron's Oloa1200). Also suitable are soya lecithin and N-vinylpyrrolidone polymers.Also suitable are sodium salts of phosphated monoglycerides anddiglycerides with saturated and unsaturated substituents, AB diblockcopolymers of A: polymers of 2-(N;N)di-methylaminoethyl methacrylatequaternized with methyl p-toluenesulfonate, and B: poly-2-ethylhexylmethacrylate. Also suitable, especially in liquid toners, are divalentand trivalent carboxylates, especially aluminum tristearate, bariumstearate, chromium stearate, magnesium octoate, calcium stearate, ironnaphthalite and zinc naphthalite. Also suitable are chelating chargecontrol agents (EP 0 636 945 A1), metallic (ionic) compounds (EP 0 778501 A1), phosphate metal salts, such as described in JA 9 (1997)-106107.Also suitable are azines of the following Colour Index Numbers: C.I.Solvent Black 5, 5:1, 5:2, 7, 31 and 50; C.I. Pigment Black 1, C.I.Basic Red 2 and C.I. Basic Black 1 and 2.

The layered double hydroxides used in accordance with the invention areincorporated individually or in combination with one another or withfurther charge control agents, mentioned above, in a concentration offrom 0.01% to 50% by weight, preferably from 0.05% to 20% by weight,with particular preference from 0.1% to 5.0% by weight, based on theoverall mixture, into the binder of the respective toner, developer,coating material, powder coating material, electret material or of thepolymer which is to be electrostatically separated, said incorporationbeing homogeneous and taking place, for example, by means of extrusionor kneading, beadmilling or using an Ultraturrax (high-speed stirrer).In this context the compounds employed in accordance with the inventioncan be added as dried and milled powders, dispersions or solutions,presscakes, masterbatches, preparations, made-up pastes, as compoundsapplied from aqueous or nonaqueous solution to appropriate carriers suchas silica gel, TiO₂, Al₂O₃ or carbon black, for example, or mixed withsuch carriers, or added in some other form. Similarly, the compoundsused in accordance with the invention can also in principle be addedeven during the preparation of the respective binders, i.e., in thecourse of their addition polymerization, polyaddition orpolycondensation, and also in the preparation of polymerization toners,during the suspension or emulsion polymerization or in the aggregationof the polymer systems to toner particles, for example.

The charge control agents of the invention can also be used in the formof fine aqueous, aqueous-organic or organic dispersions. The particlesizes (d₅₀ values) are between 20 nm and 1 μm, preferably between 50 and500 nm. Advantageous concentrations of charge control agents are between0.01% and 50% by weight, preferably between 0.1% and 30% by weight,based on the total weight of the dispersion. The viscosity of such adispersion is advantageously between 0.5 and 106 mPa s, preferablybetween 1 and 5000 mPa s. In the case of aqueous or aqueous-organicdispersions it is preferred to use water in the form of distilled ordeionized water. In the case of organic or aqueous-organic dispersionsthe organic medium used comprises one or more organic solvents,preferably from the group of monohydric or polyhydric alcohols, theirethers and esters, e.g., alkanols, particularly those having 1 to 4carbon atoms, such as methanol, ethanol, propanol, isopropanol, butanoland isobutanol, for example; dihydric or trihydric alcohols, especiallythose having 2 to 6 carbon atoms, examples being ethylene glycol,propylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol,1,6-hexanediol, 1,2,6-hexanetriol, glycerol, diethylene glycol,dipropylene glycol, triethylene glycol, polyethylene glycol,tripropylene glycol and polypropylene glycol; lower alkyl ethers ofpolyhydric alcohols, such as ethylene glycol monomethyl or ethyl orbutyl ether, triethylene glycol monomethyl or ethyl ether; ketones andketone alcohols, such as acetone, methyl ethyl ketone, diethyl ketone,methyl isobutyl ketone, methyl pentyl ketone, cyclopentanone,cyclohexanone and diacetone alcohol; and amides, such asdimethylformamide, dimethylacetamide and N-methylpyrrolidone, forexample. For the preparation of stable dispersions it is possible inaddition to use customary ionic or nonionic dispersing assistants,examples being sulfonates, phosphates, polyphosphates, carbonates,silicates, hydroxides, metal soaps, polymers, such as acrylates, fattyacid derivatives and glycoside compounds. The dispersions may furthercomprise metal complexing agents, such as EDTA or NTA, for example.

The dispersions may further comprise customary additives as well,examples being preservatives, biocides, antioxidants, cationic, anionic,amphoteric or nonionic surface-active substances (surfactants andwetting agents), devolatilizers/defoamers, and viscosity regulators,e.g., polyvinyl alcohol, cellulose derivatives or water-soluble naturalor synthetic resins and polymers as film formers, or binders forincreasing the adhesion and abrasion resistance. pH regulators employedinclude organic or inorganic bases and acids. Preferred organic basesare amines, such as ethanolamine, diethanolamine, triethanolamine,N,N-dimethylethanolamine, diisopropylamine, aminomethylpropanol ordimethylaminomethylpropanol. Preferred inorganic bases are sodium,potassium or lithium hydroxide or ammonia. Further constituents may behydrotropic compounds, such as formamide, urea, tetramethylurea,ε-caprolactam, ethylene glycol, diethylene glycol, triethylene glycol,polyethylene glycol, butyl glycol, methyl cellosolve, glycerol, sugars,N-methylpyrrolidone, 1,3-diethyl-2-imidazolidinone, thiodiglycol, sodiumbenzenesulfonate, Na xylenesulfonate, Na toluenesulfonate, Nacumenesulfonate, Na benzoate, Na salicylate or Na butyl monoglycolsulfate. The concentration of these dispersing assistants and/orcustomary additives in the dispersion is advantageously between 0.001%and 80% by weight, preferably between 0.01% and 50% by weight, based onthe total weight of the dispersion.

In order to prepare electrophotographic color toners colorants are addedsuch as organic chromatic pigments, inorganic pigments or dyes, usuallyin the form of powders, dispersions, presscakes, solutions ormasterbatches. The organic chromatic pigments can be from the group ofthe azo pigments or polycyclic pigments or can be mixed crystals (solidsolutions) of such pigments.

Preferred blue pigments and/or green pigments are copperphthalocyanines, such as C.I. Pigment Blue 15,15:1, 15:2, 15:3,15:4,15:6, P. Blue 16 (metal-free phthalocyanine), or phthalocyanineswith aluminum, nickel, iron or vanadium as the central atom, and alsotriarylcarbonium pigments, such as Pigment Blue 1, 2, 9, 10, 14, 62, 68;Pigment Green 1, 4, 7, 45; orange pigments, such as P.O. 5, 13, 34, 36,43, 62, 71; yellow pigments, such as P.Y. 12, 13, 14, 17, 74, 83, 93,97, 111, 120, 122, 139, 151, 154, 155, 174, 175, 176, 180, 174, 185,194, 213, 214; red pigments, such as P.R. 2, 3, 4, 5, 9, 38, 48, 53, 57,112, 122, 144, 146, 147, 149, 168, 170, 175, 176, 177, 179, 181, 184,185, 186, 188, 189, 202, 207, 208, 209, 210, 214, 219, 238, 253, 254,255, 256, 257, 266, 269, 270, 272, 279; violet pigments such as P.V. 1,19, 23, 32; carbon blacks such as P. Black 7, 11, 33 or in theirsurface-modified form as described in U.S. Pat. No. 5,554,739,iron/manganese oxides; and also mixed crystals such as those, forexample, of pigments described above such as C.I. Pigment Violet 19 andC.I. Pigment Red 122, and also azo-surface-modified pigments asdescribed in WO 01/30919.

The mixtures can be prepared in the form of powders, by mixingpresscakes, spray-dried presscakes or masterbatches and also bydispersing (extrusion, kneading, roll-mill processes, bead mills,Ultraturrax, ultrasound) in the presence of a carrier material in solidor liquid form (aqueous and nonaqueous inks) and also by flushing in thepresence of a carrier material. Where the colorant is used with highproportions of water or solvent (>5%) mixing can also take place atelevated temperatures, by subsequent cooling of the mixture mass andwith vacuum assistance. The flushing operation can take place in thepresence or absence of organic solvents and of waxes.

Particularly appropriate for increasing the brightness but also forshading the hue are mixtures with organic dyes. Preferred such dyesinclude the following: water-soluble dyes, such as Direct, Reactive andAcid Dyes, and also solvent-soluble dyes, such as Solvent Dyes, DisperseDyes and Vat Dyes. Examples include the following: C.I. Reactive Yellow37, Acid Yellow 23, Reactive Red 23, 180, Acid Red 52, Reactive Blue 19,21, Acid Blue 9, Direct Blue 199, Solvent Yellow 14, 16, 25, 56, 62, 64,79, 81, 82, 83, 83:1, 93, 98,133, 162, 174, Solvent Red 8, 19, 24, 49,89, 90, 91, 92, 109, 118, 119, 122, 124, 127, 135, 160, 195, 212, 215,Solvent Blue 44, 45, Solvent Orange 41, 60, 63, Disperse Yellow 64, VatRed 41, Solvent Black 45, 27.

It is also possible to use dyes and pigments having fluorescentproperties, such as ®Luminols (Riedel-de Haen), in order for example toproduce anticounterfeit toners.

Additionally the colorants may also be used in a special wax-coatedform, as described in EP-A-1 204 005, in combination with the chargecontrol agents of the invention.

Inorganic pigments, such as TiO₂ or BaSO₄, for example, are used inmixtures for lightening. Also suitable are mixtures with effectpigments, such as pearlescent pigments, Fe₂O₃ pigments (®Paliocroms),and pigments based on cholesteric polymers, which exhibit differentcolors depending on the angle of observation.

Electrophotographic toners and also powder coating materials may furthercomprise waxes. The term “wax” denotes a range of substances, naturallyor synthetically obtained, which generally have the followingproperties: they are kneadable at 20° C., range from firm to hard andfragile, from coarse to finely crystalline, and from translucent toopaque, but not grasslike; they melt without decomposition above 40° C.,are of relatively low viscosity, without stringing, at just a littleabove the melting point, have a highly temperature-dependent consistencyand solubility, and can be polished under gentle pressure (cf. UllmannsEnzyklopädie der technischen Chemie, Volume 24, 4th Edition 1983, pp.1-49, Verlag Chemie, Weinheim and Römpps Chemie-Lexikon, Volume 6, 8thEdition 1988, p. 463, Franck'sche Verlagshandlung).

The following waxes are preferred: natural waxes, such as plant waxes,e.g., carnauba wax, candellila wax, and animal waxes, e.g., beeswax,modified natural waxes, such as paraffin waxes, microwaxes,semisynthetic waxes, such as montan ester waxes, or synthetic waxes,such as polyolefin waxes, e.g., polyethylene and polypropylene waxes,polyethylene glycol waxes, cycloolefin copolymer waxes, amide waxes,such as N,N′-distearylethylenediamine, zirconocene waxes, andchlorinated or fluorinated polyolefin waxes orpolyethylene-polytetrafluoroethylene wax mixtures.

Particular preference is given to polyolefin waxes, and also topolyolefin waxes containing polar groups, formed by subsequent oxidationof the polyolefin wax, by grafting reaction with monomers containingcarboxylic acid, carboxylic ester, carboxylic anhydride or hydroxylgroups or by copolymerization from an olefin and a monomer containingcarboxylic acid, carboxylic ester, carboxamide, carboxylic anhydride orhydroxyl groups.

Waxes in the context of the present invention may also be compounds ofrelatively high molecular mass which have a waxlike character and havebeen prepared preferably by polycondensation, polyaddition or additionpolymerization processes, examples being thermoplastic polyester resins,epoxy resins, styrene-acrylate copolymer resins, styrene-butadienecopolymer resins and cycloolefin copolymer resins, such as ®Topas, forexample. In order to possess sufficient solubility at elevatedtemperature in organic solvents such polymers generally possess anumber-average molecular weight ({overscore (M)}_(n)) of from 500 up to20 000. Preferred waxes are those having a number-average molecularweight ({overscore (M)}_(n)) of from 800 up to 10 000, particularpreference being given to those having a number-average molecular weight({overscore (M)}_(n)) of from 1000 up to 5000.

The dropping point of the waxes used in accordance with the invention orthe softening temperature of said waxlike polymers is preferably in therange from 20 to 180° C., more preferably in the range from 30 to 140°C.

The present invention also provides an electrophotographic toner, powderor powder coating material containing from 30% to 99.99% by weight,preferably from 40% to 99.5% by weight, of a customary binder, such as astyrene, styrene-acrylate, styrene-butadiene, acrylate, urethane,acrylic, polyester or epoxy resin or a combination of the last two, from0.01% to 50% by weight, preferably from 0.05% to 20% by weight, morepreferably from 0.1% to 5% by weight, of at least one salt of layereddouble hydroxides, as described above, and, if desired, from 0.001% to50% by weight, preferably from 0.05% to 20% by weight, of a colorant,based in each case on the total weight of the electrophotographic toner,powder or powder coating material.

The compounds described in accordance with the invention may also beapplied to free-flow agents as an additional charge control agent insuspended form or in a dry blend. The compounds described in accordancewith the invention can also be used for a carrier coating.

In the examples which follow, parts and percentages are by weight.

PREPARATION EXAMPLE 1

10 g of Mg—Al hydroxide carbonate (stoichiometric Mg:AI ratio=2:1)(Syntal HSA 696, Sudchemie, Germany) are dispersed by stirring in 100 mlof deionized water at 60 to 80° C. for 1 hour. Then a solution of 3 g ofbenzoic acid in 100 ml of deionized water is prepared with the additionof sodium hydroxide to a pH of approximately 8 and is added to the Mg—Alhydroxide carbonate suspension. The mixture is stirred at 70° C. for 6hours, the suspension is filtered, the solid product is washedrepeatedly with deionized water and then the washed solid is dried invacuo at 60-80° C.

PREPARATION EXAMPLE 2

10 g of calcined Mg—Al hydroxide carbonate (stoichiometric Mg:AIratio=2:1) (Syntal HSAC 701, Sudchemie, Germany) are dispersed bystirring in 100 ml of deionized water at 60° C. for 1 hour. Then asolution of 3 g of 4-toluenesulfonic acid in 100 ml of deionized wateris prepared and is added to the Mg—Al hydroxide carbonate suspension.The mixture is stirred at 80° C. for 30 hours, the suspension isfiltered, the solid product is washed repeatedly with deionized waterand then the washed solid is dried in vacuo at 70° C.

PREPARATION EXAMPLES 1 TO 14

Ex. No. Double hydroxide Anion A 1 Syntal HSA 696 benzoic acid 2 SyntalHSAC 701 4-toluenesulfonic acid 3 Syntal HSA 696 dithiodisalicylic acid4 Sorbacid 911, Südchemie relatively long-chain carboxylic acid (Mg:Al =2:1) 5 Syntal HSAC 701 (calcin.) citric acid 6 Syntal HSAC 701 (calcin.)lactic acid 7 Syntal HSAC 701 (calcin.) glycolic acid 8 Syntal HSAC 701(calcin.) tartaric acid 9 Syntal HSAC 701 (calcin.)dodecylbenzenesulfonic acid 10 Syntal HSAC 701 (calcin.) NaC₁₂/C₁₄-alkyl-triglycol ether sulfate 11 Syntal HSAC 701 (calcin.)naphthalene-2-sulfonic acid 12 Syntal HSAC 701 (calcin.) 1-naphthoicacid 13 Syntal HSAC 701 (calcin.) decanoic acid 14 Syntal HSAC 701(calcin.) hexanoic acid

APPLICATION EXAMPLE 1

1 part of the compound from preparation example 1 is incorporatedhomogeneously using a kneading apparatus over the course of 30 minutesinto 99 parts of a toner binder (styrene-acrylate copolymer 60:40®Almacryl B-1501). The composition is then ground on a universallaboratory mill and subsequently classified in a centrifugal classifier.The desired particle fraction (4 to 25 μm) is activated with a carriercomposed of magnetite particles coated with styrene-methacrylatecopolymer (90:10) and measuring 50 to 200 μm.

APPLICATION EXAMPLE 2

The procedure of application example 1a is repeated but using instead ofthe styrene-acrylate copolymer a polyester resin based on bisphenolA®Fine Tone 382-ES) and as carrier silicone-coated ferrite particlesmeasuring 50 to 200 μm.

Measurement takes place on a standard q/m measurement stand. By using asieve having a mesh size of 45 μm it is ensured that no carrier isentrained when the toner is blown out. The measurements are made atabout 50% relative atmospheric humidity. As a function of the activationperiod the q/m values [μC/g] which follow are measured: Applicationexample Activation 1 2 period Charge q/m [μC/g] 5 min. −10 −23 10 min.−10 −23 30 min. −11 −24 2 h −12 −27

APPLICATION EXAMPLES 3 TO 15

The procedure of application example 2 is repeated, but using instead ofthe compound from preparation example 1 the compounds listed below. Ex.q/m [μC/g] No. compound employed 5 min. 10 min. 30 min. 2 hrs 3preparation example 2 −21 −23 −25 −26 4 preparation example 3 −22 −23−25 −25 5 preparation example 4 −19 −22 −27 −30 6 preparation example 5−16 −17 −17 −18 7 preparation example 6 −19 −19 −20 −17 8 preparationexample 7 −18 −19 −20 −19 9 preparation example 8 −16 −18 −19 −16 10preparation example 9 −6 −4 −4 −4 11 preparation example 10 −8 −6 −4 −312 preparation example 11 −20 −23 −26 −25 13 preparation example 12 −19−24 −28 −30 14 preparation example 13 −20 −22 −24 −25 15 preparationexample 14 −22 −25 −28 −29

1. A process for controlling the charge of an electrophotographic toner,electrophotographic developer, powder, powder coating material, electretmaterial or a chargeable material in an electrostatic separation processcomprising the step of adding at least one charge control agent to theelectrophotoqraphic toner, electrophotographic developer, powder, powdercoating material, electret material or the chargeable material in anelectrostatic separation process, wherein the at least one chargecontrol agent is a layered double hydroxide salt and wherein the doublehydroxide salt comprises at least one of monovalent and divalent metalcations trivalent metal cations, and organic anions A of the formulae(XIII)

wherein R¹⁸, R¹⁹ and R²⁰ are identical or different and are hydrogen,C₁-C₂₂-alkyl, C₁-C₁₈-alkenyl, C₁-C₁₈-alkoxy;

wherein R is hydrogen, C₁-C₄-alkyl, C₁-C₄-alkoxy or halogen.
 2. Theprocess as claimed in claim 1, wherein as organic anions are anions froman acid selected from the group consisting of: benzoic acid, naphthoicacid, 4-tert-butylbenzoic acid, benzenesulfonic acid, p-toluenesulfonicacid, naphthalenesulfonic acid, and 2,2′-dithiobenzoic acid.
 3. Theprocess as claimed in claim 1, wherein the number of hydroxyl groups isfrom about 1.8 to 2.2 times the sum of all the metal cations.
 4. Theprocess as claimed in claim 1, wherein monovalent metal cations presentare selected from the group consisting of Li⁺, Na+ and K⁺.
 5. Theprocess as claimed in claim 1, wherein the at least one double hydroxidesalt contains Mg²⁺ and Al³⁺.
 6. The process as claimed in claim 5,wherein the molar ratio Mg²⁺: Al³⁺+s from 3.1:1 to 1:2.
 7. The processas claimed in claim 1, wherein the at least one double hydroxide salt isa calcined hydrotalcite.
 8. The process as claimed in claim 1, whereinthe adding step further comprises adding one or more charge controlagents selected from the group consisting of triphenylmethanes; ammoniuma compounds, immonium compounds, iminium compounds; fluorinated ammoniumcompounds, fluorinated immonium compounds; biscationic acid amides;polymeric ammonium compounds; diallylammonium compounds; aryl sulfidederivatives, phenol derivatives; phosphonium compounds, fluorinatedphosphonium compounds; calix[n]arenes, cyclically linkedoligosaccharides, derivatives of cyclically linked oligosaccharides, inparticular boron ester derivatives, interpolyelectrolyte complexes;polyester salts; metal complex compounds, salicylate-nonmetal complexes,salts of ionic structured silicates, hydroxycarboxylic acid-metalcomplexes hydroxycarboxylic acid-nonmetal complexes, benzimidazolones;azines, thiazines and oxazines.
 9. The process as claimed in claim 1,wherein the at least one charge control agent is present in aconcentration of from 0.01% to 50% by weight, based on the total weightof the electrophotographic toner, electrophotographic developer, powder,powder coating material, electret material or chargeable material forelectrostatic separation.
 10. An electrophotographic toner, powder orpowder coating material, containing from 30% to 99.99% by weight of abinder, from 0.01% to 50% by weight of at least one layered doublehydroxide salt as set forth in claim 1, and, optionally, from 0.001% to50% by weight of a colorant, based on the total weight of theelectrophotographic toner, powder or powder coating material.
 11. Theprocess as claimed in claim 1, wherein the divalent metal cations areselected from the group consisting of Mg²⁺, Ca²⁺, Zn²⁺, Co²⁺, Ni²⁺,Fe²⁺, Cu²⁺ and Mn²⁺.
 12. The process as claimed in claim 1, wherein thetrivalent metal cations are selected from the group consisting of A ³⁺,Fe³⁺, Co³⁺, Mn³⁺, Ni³⁺, Cr³+ and B³⁺.
 13. The process as claimed inclaim 8, wherein the metal complex compound is a salicylate metalcomplex.
 14. An electrophotographic toner, electrophotographicdeveloper, powder, powder coating material, electret material orchargeable material for an electrostatic separation process made inaccordance with the process of claim 1.